1. Field of the Invention
The present invention relates generally to industrial cleaning mechanisms and devices, and more specifically to an apparatus for applying a scraping blade to a conveyor belt for scraping material therefrom during the operation of the belt. The present invention provides a means for applying an even, uniform scraper pressure across the entire width of the belt, thus eliminating uneven scraping due to sag of the scraper blade. A lower scraper pressure is also required, allowing the use of a relatively soft scraper blade material to reduce greatly the wear and tear on the belt. Two different embodiments are disclosed herein, with the first embodiment directed to a secondary type belt wiper or cleaner, which operates across a free span of the belt, and the second embodiment directed to a primary type belt wiper, which operates across the belt as it passes over a roller.
2. Description of the Related Art
Conveyor belts are used in many different industries (mining, maritime, food processing, etc.) for the conveyance or transfer of raw materials or finished goods from one point to another. Such conveyors, particularly when used for raw materials, generally become contaminated with the materials and require the removal of such material buildup from time to time, in order to avoid contaminating or jamming the equipment.
Accordingly, various devices have been developed for cleaning or scraping down the surface of a conveyor belt. While most such devices provide some moderate success, it must be considered that most were developed for relatively narrow conveyor belts, having a width on the order of about three feet. As such, there is relatively little lateral sag across the belt, and/or across the laterally disposed cleaner or scraper blade. However, with the development of relatively wider conveyor belts for greater productivity, such earlier devices are generally incapable of providing a thorough cleaning or scraping action across the entire width of the belt. Many such belts now have widths of seven to eight feet, and while earlier scrapers have been scaled up to reach across such relatively wide belts, they do not provide the even pressure across the entire width of the belt which is necessary for thorough cleaning of the belt.
Moreover, many such earlier scrapers utilize relatively thin metal scraping blades. This, along with the relatively high scraping pressure required in order to assure scraping action across the entire width of the belt, can result in uneven pressures and possible cutting or scoring of the belt, leading to further difficulty in cleaning the belt and early replacement of the belt.
Accordingly, a need will be seen for a cleaner or scraping device for conveyor belts, which applies an even and uniform pressure across the entire belt by means of fluid activation. The device also includes a single, relatively wide scraper blade of relatively soft material, in order to impart such even and uniform pressures across the entire width of the belt and to avoid cutting or grooving the belt during the scraping operation. The depth of the blade is sufficient to preclude significant distortion or bending thereof, with all forces imparted between the conveyor belt and the scraper blade being evened out by the fluid actuation of the blade. A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,696,388 issued on Sep. 29, 1987 to Donald L. Stoll, titled "Conveyor Belt Scraper Blade Assembly With Contoured Surface," describes a scraper having a convex transverse contour, for applying scraping pressure across the center of a conveyor belt having a concave lateral shape due to use and the belt support system. The scraper blades are formed of relatively soft materials (i.e., different rubber durometers), but the Stoll device does not apply an even pressure completely across the belt if the belt does not precisely match the contour of the blade of the device. This is particularly true for a primary type belt cleaner, where the scraper spans the belt across a supporting roller for the belt, which does not allow the belt to flex. Stoll does not disclose any fluid pressure actuating means for his scraper assembly, as is provided by the present invention.
U.S. Pat. No. 5,113,999 issued on May 19, 1992 to Reiner Zeppenfeld, titled "Positionable Doctor Blade," describes an apparatus for applying pressure to an opposed pair of doctor blades or scrapers each bearing against one of a pair of opposed belts on corresponding rollers, i.e., primary wipers or blades. The mechanism used to apply pressure to the blades may utilize fluid pressure (i.e., hydraulic or pneumatic), but the pressure actuator operates only a single arm which is in turn connected between the two blades to apply equal pressure to the two blades. Zeppenfeld does not provide any means for applying even pressure along the entire length of a single blade, as each of his single blades is held in place in a rigid mechanical linkage. Zeppenfeld does not utilize an inflatable bladder disposed transversely along the entire back of the blade for applying uniform pressure to the entire blade across the entire width of the conveyor, as provided by the present invention.
U.S. Pat. No. 5,213,197 issued on May 25, 1993 to Toyoshige Mohri, titled "Belt Cleaner For Conveyor," describes a fluid activated scraper blade array. A transverse bladder is used to apply pressure to a series of blades, which in turn apply scraping pressure to the surface of the conveyor. The blades are tied together by a flexible cover sheet secured to each side thereof. Thus, each blade is somewhat independent of every other blade, particularly for blades which are somewhat laterally separated from one another. In contrast, the present conveyor scraper mechanism uses a single scraper blade which extends essentially the entire width of the conveyor belt to provide a uniform pressure completely thereacross. Also, Mohri utilizes a relatively hard and narrow, sharp material for his blade segments, as opposed to the relatively soft plastic single blade element of the present invention.
U.S. Pat. No. 5,248,026 issued on Sep. 28, 1993 to Allen J. Morefield, titled "Conveyor Belt Scraper Mechanism," describes a fluid actuated mechanism having a single fluid cylinder which in turn actuates an arm which rotates a blade toward or away from the belt. The resulting action is somewhat related to that described in the '999 U.S. patent to Zeppenfeld, described further above, in that the linkage which applies the scraping pressure to the blade is mechanical. Moreover, Morefield utilizes a relatively hard metal blade, unlike the relatively soft plastic material used for the blade of the present scraper invention. Morefield does not disclose an inflatable bladder extending essentially the entire
U.S. Pat. No. 5,372,244 issued on Dec. 13, 1994 to Normand J. Morin, titled "Conveyor Belt Scraper," describes a fluid expelled plastic scraper blade. The blade is coiled within a chamber, and water under high pressure is forced into the chamber to push the blade from the chamber to compensate for blade wear. Morin does not utilize an inflatable bladder to apply continuous even pressure to the blade against the conveyor belt, as provided by the present invention.
U.S. Pat. No. 5,622,249 issued on Apr. 22, 1997 to Normand J. Morin, titled "Conveyor Belt Scraper," describes a system essentially like that described immediately above in the '244 U.S. patent to the same inventor. The '249 U.S. patent also describes a suspension system for the blade and blade housing, which has no bearing on the present belt scraper invention.
U.S. Pat. No. 5,722,528 issued on Mar. 3, 1998 to Troy D. Dolan, titled "Method And Apparatus For Cleaning Conveyor Belts," describes a device having a transverse support for a plurality of individual blade lift cylinders and corresponding plurality of blades. The Dolan device is exceedingly complex, as it requires a myriad of separate pressure and return lines to feed all of the cylinders of the device. In contrast, the present invention utilizes a single fluid lift mechanism comprising a flexible bladder (not a rigid cylinder), which in turn applies pressure to the edge (in one embodiment) or to the opposite side (in a second embodiment) of a single, relatively wide scraper blade formed of a relatively soft material (i.e., plastic).
Finally, International Patent Publication No. 94/08875 published on Apr. 28, 1994 to Normand J. Morin, titled "Conveyor Belt Scraper," describes a scraper comprising a sheet of flexible plastic which is coiled within a pressurized cylinder. One edge of the plastic extends from a slot in the cylinder, and is forced from the slot and against the conveyor belt by pressurizing the cylinder. The '875 International Patent Publication to Morin is based upon a British patent application, upon which the '249 U.S. patent to the same inventor (discussed further above) is based. The '875 International Patent Publication is also closely related to the '244 U.S. patent to the same inventor, also discussed further above. The same distinctions are felt to apply here.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.